This invention relates to a mass spectrometer in which secondary ions can be used to analyze insulators.
A mass spectrometer comprises an ion gun for radiating an ion beam onto a surface of an object to make the surface emit secondary ions having an energy distribution. The secondary ions' energy distribution has a peak and a "specific energy bandwidth" defined with reference to the peak in a manner which will later be described more in detail.
The mass spectrometer further comprises a detector for ions and a directing member for directing secondary ions having energies coming within an analyzable energy range of the mass spectrometer to the detector. In a conventional mass spectrometer, its analyzable energy range has a width nearly equal to the specific energy bandwidth of the secondary ions. However, with this structure it is difficult to analyze an insulator, although a conductor can be analyzed. This is because for an insulator the energy distribution of the secondary ions becomes inconveniently shifted, as will be explained below.